Hybrid power devices are used in many electronic designs. For example, radio frequency communications devices, such as cellular telecommunications devices, use hybrid power devices such as hybrid power amplifiers. As cellular telecommunications devices offer users a wider array of features, more circuitry is needed to implement these features, and thus a demand for more powerful hybrid amplifiers has arisen. For example, in 1997 radio frequency devices typically employed a hybrid amplifier that provided from 10 to 30 Watts of power. However, by the end of 1998, engineers were designing devices that were demanding hybrid power amplifiers which could provide power in the range of 80-120 Watts of power, and it was apparent that even more powerful amplifiers would be required in the near future to accommodate even more telecommunications features.
Power amplification in a hybrid power amplifier is accomplished through the use of hybrid transistors that are also called cells. The power output of a single cell is limited, and so to increase the power output of a hybrid power amplifier, more cells must be used in a device. The clustering or grouping of cells into a concentrated area forms what is called a die. A die may consist of any number of cells (a grouping of, for example, 28 cells is common), and groupings of cells are generally made to achieve a discrete and predictable amount of power amplification (gain).
Typically, a die is arranged in a modular unit that includes the necessary mechanical and electrical connections that link the cells to appropriate points on a hybrid power amplifier, as well as to various devices that adjust an input and an output impedance. The various devices which adjust the input and output impedance include capacitors, resistors, and connections such as wire bonds, that are chosen, in part, for their impedance. The modular unit that includes the combination of the die, it's connections, and the various devices is called a "die block." Like cells, die blocks may be grouped together (effectively increasing the number of cells) on a flange to increase the power output of a hybrid power amplifier.
FIG. 1 (prior art) illustrates a common die block 30. Generally, the die block 30 receives an input signal on input connection 32, passes the input signal from the input connection 32 through die a 38, where the input signal is processed, so that an amplified output signal may be carried from the die block 30 on output connection 33.
More specifically, input connection 32 is a conductor which is electrically connected to a metal oxide semiconductor (MOS) CAP 34 that is in turn electrically linked to a plurality of conductors called wire bonds 36 that are coupled to, and carry the input signal to, the die 38. Both the MOS CAP 34 and the wire bonds 36 bias the input impedance to match the input impedance of the die 38. The die 38 is in turn coupled to conductors called output wire bonds 37 that are connected to an output MOS CAP 35 which then is linked to the output connection 33. As was the case on the input side of the die block, the output wire bonds 37 and the output MOS CAP 35 are used to adjust the output impedance of the die block 30.
Accordingly, in operation, an input signal arrives to the die block 30 at input connection 32. The input signal travels through input connection 32 to the MOS CAP 34 that bridges the input signal to the wire bonds 36 (which function as a bias circuit by adjusting the input impedance of the circuit). Next, the input signal is then passed through the wire bonds 36 to the die 38. In the die 38 the input signal causes the die to produce an output signal which is equal to the input signal multiplied by a predetermined gain. The output signal (power output) is generated in the output wire bonds 37, and the output wire bonds 37 carry the output signal to output MOS CAP 35. Like the MOS CAP 34, the output MOS CAP 35 adjusts the output impedance of the die block 30 to more closely match the output impedance of the circuit (not shown) to which the die block 30 is connected. From the MOS CAP 35, the output signal travels off the die block 30 on the output connection 33.
FIG. 2 (prior art) illustrates a hybrid power amplifier built on a flange 10 having two die blocks 30 mounted thereon. The flange 10 has mountings 12 or other means for connecting the flange 10 to its parent RF device (not shown), which may be, for example, a cellular telephone. The flange 10 supports a substrate 15 on which various structures are disposed. For example, the flange 10 may support a bias circuit 20 comprising various resistors, capacitors and other electrical devices used to adjust the input and output impedance of the hybrid power amplifier to match the input and output impedance of the circuit to which the hybrid power amplifier is attached. The bias circuit 20 may be placed on or off the flange 10, and is illustrated in FIG. 2 as being on the flange 10 (the bias circuit 20 is represented generally as a dashed block 20 to emphasize that it may be placed on or off the flange 10). In addition, the flange 10 supports die blocks 30 (each die block 30 is shown here as a rectangle, with a dark line representing the general orientation of the die 38 in a die block 30). The flange 10 also supports additional structures, such as input/output conductors called an input pin 40 and an output pin 41, and conductors called an input transmission line 42 and an output transmission line 43. The input pin 40 and input transmission line are electrically linked. Likewise, the output pin 41 and the output transmission line 43 are also electrically coupled. The input transmission line 42, and output transmission line 43, are also coupled to the die blocks 30.
In operation, input pin 40 carries an input signal to the input transmission line 42 which then transfers the input signal to die blocks 30. The input pin 40 and the input transmission line 42 may also bias the hybrid power amplifier to match the input impedance of the circuit to which the hybrid power amplifier is connected (not shown). After processing the input signal, die blocks 30 produce the output signal. The output signal travels from the die blocks 30 to output transmission line 43, which then sends the output signal to output pin 41. The output signal travels off the flange 10 through output pin 41. Note that the die 38 on the hybrid power amplifier (and the corresponding die blocks 30) are separated by a distance S.sub.1. Note further that die blocks 30 are arranged in a single column down a vertical axis, here called the "y" axis. In this orientation, a signal "travels" generally in a horizontal path along a horizontal "x" axis, which is illustrated as a left to right travel path in FIG. 2.
As discussed above, to implement more powerful hybrid power amplifiers, more cells must be placed on each flange. Increasing the number of cells on a flange is accomplished by using larger die blocks, or by placing more die blocks on a flange. To place more die blocks on a flange, designers have taken the approach shown in FIG. 3.
FIG. 3 (prior art) illustrates a flange 10 having four die blocks 30 disposed thereon in an "in-line" arrangement. This arrangement is called "in-line" because the die blocks are arranged in a vertical line along the y-axis. The in-line flange arrangement of FIG. 3 is structurally similar to the flange arrangement FIG. 1 in that it is designed to amplify an electrical signal propagating generally from input pin 40 through the die block 30 and off the flange 10 via output pin 41. The in-line arrangement of die blocks 30 shown in FIG. 3 provides for simplicity in the design and manufacture of a hybrid power amplifier. However, the vertical in-line arrangement of the die blocks 30 across the flange 10 place the die blocks 30 in close proximity to a first perimeter 22 and a second perimeter 24. In addition, the distance between the die blocks 30 has now decreased as shown by spacing S.sub.2.
The design of FIG. 3, where die are arranged vertically on a flange, suffers several shortcomings. First, there is not enough vertical space to continue mounting additional die on the flange in the in-line arrangement, and thus, the total power output of a die seems to be mechanically limited by the vertical height (or length) of the flange 10.
Second, in operation, each cell typically generates a discrete amount of heat, and the decreased spacing between die, as indicated by S.sub.2, results in die concentrating (which means that there is less flange area between the die to be used for heat dissipation). Thus, die concentrating results in not only the concentration of cells for power, but also the concentrating of cells as heat sources. This causes the temperature of the die blocks to increase at the die, and causes the temperature of the flange at the die concentrations to increase as well (the flange typically drains heat through the mounts 12, which function as heat sinks), which may cause device failure, or even ignite the circuit. Also, though less dangerous, inefficient heat dissipation raises the temperature of surrounding electrical systems which reduces circuit efficiency.
Another disadvantage of the prior art is that die that are physically separated (such as the die in proximity to the perimeters) by random distances are often out of phase with each other electrically. Devices which are out of phase electrically suffer from unequal spacing conditions which leads to power cancellation, and thus, inefficient power transmission. Furthermore, the disadvantages of poor heat dissipation and inefficient power transmission in hybrid power devices have the consequence of reducing the bandwidth performance of the hybrid power devices.
Therefore, there exists the need for an advanced hybrid power device and method that are capable of accommodating more power amplification per flange area. The present invention provides such a device and method.